Method and system for secure server-based session management using single-use HTTP cookies

ABSTRACT

A methodology for providing secure session management is presented. After a single-use token has been issued to a client, it presents the token, and the server may identify the client based upon the presented token. However, the token may be used only once without being refreshed prior to re-use, thereby causing the token to be essentially reissued upon each use. The token comprises a session identifier that allows the issuer of the token to perform session management with respect to the receiving entity. Tokens can be classified into two types: domain tokens and service tokens. Domain tokens represent a client identity to a secure domain, and service tokens represent a client identity to a specific service. A domain token may be used with any service within a domain that recognizes the domain token, but a service token is specific to the service from which it was obtained.

This application is a continuation of application Ser. No. 09/896,195,filed Jun. 30, 2001 now U.S. Pat. No. 8,005,965, which is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improved data processing system and,in particular, to a method and apparatus for multicomputer datatransferring. Still more particularly, the present invention provides amethod and apparatus for computer-to-computer session management.

2. Description of Related Art

Information technology (IT) systems and the Internet have fueledcommercial activity. While IT systems have significant benefits, at thesame time they pose potential security threats from unauthorized thirdparties. Indeed, the lack of security in modern IT systems has emergedas a threat to the integrity of global computer networks.

To deal with this problem, IT systems provide a number of knownservices: data authentication, data confidentiality, entityauthentication, and entity authorization. Data authentication typicallyconsists of two sub-services: data integrity and data originauthentication. A data integrity service is used to convince a receiverof some item of given data that the data was not changed during transit,and data origin authentication proves to the receiver the identity ofthe real sender. Data confidentiality protects against disclosure ofdata during transmission. Entity authentication provides a system withproof that a certain entity is who they claim to be.

Authorization is the act of determining whether an authenticated entityhas the right to execute an action. Authorization and authenticationthus are dual services. To be able to provide authorization, it isnecessary to determine who the entity is, e.g., by entityauthentication. Authorization, in general, consists of two separatestages: the provision of privileges to a particular entity, e.g.,authorization credentials, and the use of these privileges by thereceiving entity in combination with access decision rules at aprotected service or a protected resource to determine if access shouldbe granted to the entity.

The client-side applications of many IT systems are now based on a Webbrowser application architecture because of its adaptability to multipleuses. Through the standard Hypertext Transfer Protocol (HTTP), a user ofa browser application on a client machine can gain access to resourcesor services on any HTTP-enabled server. If the user at the clientdesires to access a protected resource or a protected service at theserver that can only be accessed by an authenticated and authorizeduser, however, there must be some process to authenticate and authorizethe user/client.

As is well-known, a cookie is a data item that is stored on a client bya server through a particular user's web browser. When a user of aclient machine visits a Web server, the server may return a cookie tothe user's browser to be stored in a client-side cookie cache. When acookie is “set”, i.e. stored, as part of an HTTP transaction, it mayinclude the path, i.e. domain, for which the cookie is valid, thecookie's name and value, and other optional attributes, such as thecookie's expiration date. In most cases, the client browserautomatically stores the cookie data by default, sometimes withoutgiving the user the option or the knowledge of it being done. When theuser revisits the server at some later point in time, the cookie is sentwith the request, thereby identifying the user to the server.

A typical cookie can be quite convenient for identifying a user orclient to a server, but depending on the type of resources and servicesprovided by a server, a cookie introduces security vulnerabilities intoclient-server communications. In some prior art solutions,identification data is forwarded within a cookie when the client browserissues a request for a protected resource to the server that set thecookie. Such an approach can be insecure because an attacker thatobtains possession of the cookie might be able to gain userauthorization to access the protected resource. In other words, aninsecure implementation of a cookie might equate proof of possessionwith proof of identity. In fact, some servers equate possession of acookie with authentication of the identity of the client/user thatpossesses the cookie, thereby relying on the cookie as a short-cut foridentifying a user or client by other means even though cookies may bestolen and then used maliciously. More insidiously, some cookieimplementations also contain the username and password required by auser to authenticate into a system. This is particularly dangerousbecause if this information is stolen, a malicious user can authenticateto a system using other means, such as a login application, and therebyappear to be the user that is being impersonated. The malicious usercould thereafter have his own cookies set by the server at the malicioususer's client machine.

Cookies can be either persistent cookies, which are stored on disk, ormemory cookies, which are stored in memory. Persistent cookies reside ina client file or cookie cache, such as “cookies.txt”, after the clientbrowser is closed and are available during the next browser session.Memory cookies disappear when the browser is shut down. However, bothtypes of cookies can be dangerous since both types of cookies can bestolen by malicious code, such as a JavaScript that has a Trojan horse,i.e. benign code that hides malicious code, through interception ofnetwork traffic, or by a malicious server in the cookie's intendeddomain of use. Although both types of cookies are vulnerable to theft,persistent cookies are a bigger threat because they can be stolen fromthe cookie file. As a consequence, these prior art schemes are highlysusceptible to replay attacks wherein one who acquires a cookie cansimply assert it to gain access to a protected resource or protectedservice.

As mentioned above, applications in many IT systems are increasinglyusing Web-based or Internet-based standards, such as HTTP. However, HTTPis a stateless protocol—each client request to a server establishes aconnection between the client and the server, but according to a strictinterpretation of the HTTP standard, the connection is considered closedwhen the server responds to the client request. The client mayimmediately generate another request to the server, but the subsequentrequest is considered to establish another connection. Obviously, themost common interactions between a client and a server require multiplerequests that are related to each other and that the server needs toknow are related to one another. In other words, the server needs tomaintain a session context for each client through which it determinesthat a request from a client is related to a previous request andrequires a response based on this temporal relationship. Hence, mostservers need a session management mechanism.

Due to the round-trip nature of a cookie being issued from a server to auser or client and then being returned to the server at a later point intime, cookies provide a degree of state to HTTP. Therefore, cookies arefrequently used for session management purposes within the server thatissued the cookie.

Although session management within the server is facilitated or enabledby the use of cookies, the use of cookies for secure session managementhas been historically problematic because of the client-sidevulnerabilities that were discussed above with respect toauthentication. Since cookies are supported by all commercial Webbrowsers and servers, cookies are frequently used for detailed sessionmanagement, such as tracking user movement within Web sites. From asecurity standpoint, however, a computational environment that employscookies to enable secure access to protected resources and/or serviceswhile storing cookies in cookie caches creates vulnerabilities that areexploitable via the acquisition of cookies by malicious persons.

Other alternative security methodologies rely heavily on client-sidefunctionality, but most suffer from the fundamentally uncontrollednature of most client-based systems. The infrastructure required tosupport these client systems and to maintain a secure trust chain amongtheir components is considered to be unwieldy in many environments.

Therefore, it would be advantageous to have a lightweight securitysolution for ongoing session management in a Web environment. It wouldbe particularly advantageous to have a method and system forcookie-based secure session management that is server-based and iscompliant with existing Internet protocols.

SUMMARY OF THE INVENTION

The present invention is a method, system, apparatus, or computerprogram product for providing secure session management using single-usetokens, also termed single-use cookies. After a single-use token hasbeen issued to an entity, the entity may present the token to a service,and the receiving entity may identify the presenting entity based uponthe presented token. However, the token may be used only once, afterwhich the token must be updated or refreshed prior to re-use, therebycausing the token to be essentially reissued upon each use. The tokencomprises a session identifier of some sort that allows the issuer ofthe token to perform session management with respect to the receivingentity.

Tokens can be classified into two types: domain tokens and servicetokens. Domain tokens represent a client identity to a secure domain,and service tokens represent a client identity to a specific service,but both domain tokens and service tokens can be implemented as a cookiein accordance with common protocols for obtaining and setting cookiesfor a client browser. A domain token may be used with any service withina domain that recognizes the domain token in order to obtain a servicetoken, but a service token is specific to the service from which it wasobtained; a service token may not be used with any services other thanthe one that created it.

A client attempts to login to a domain through a first server, whichchallenges the client to provide authentication data for identifying theclient or the user of the client. After the first server hasauthenticated the client or the user of the client, the first servergenerates a single-use domain token that is associated with the clientor the user of the client and returns the single-use domain token to theclient. The login request may have originated as a redirect responsefrom a second server; if so, then the first server redirects the clientto the second server.

At some point in time, a client sends to the second server a request toaccess a protected resource. If the client already possesses asingle-use domain token, then the single-use domain token is sent to thesecond server along with the request to access the protected resource.If the second server does not also receive a single-use domain token,then the client is redirected to the first server to complete the domainlogin process.

If the client already possesses a single-use service token, then thesingle-use service token is also sent to the second server along withthe request to access the protected resource. If not, then the secondserver attempts to issue a single-use service token for the client orthe user of the client, and the single-use service token is sent to theclient along with the response to the request to access the protectedresource. If a single-use service token is also received with therequest to access the protected resource, the single-use service tokenis validated prior to generating the response to the request to accessthe protected resource.

This summary outlines some of the features of the present inventionwhich are illustrative of the invention, and a fuller understanding ofthe invention may be had by referring to the Detailed Description.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, further objectives,and advantages thereof, will be best understood by reference to thefollowing detailed description when read in conjunction with theaccompanying drawings, wherein:

FIG. 1A depicts a typical network of data processing systems, each ofwhich may implement the present invention;

FIG. 1B illustrates a Web-based environment in which the presentinvention may be implemented;

FIG. 1C is a data flow diagram illustrating a prior art process that maybe used when a client attempts to access a protected resource;

FIG. 2A is a block diagram depicting the primary entities that areinvolved in an environment that implements the present invention;

FIG. 2B is a block diagram depicting a domain authentication processbetween a client and a Cookie Distribution Center (CDC);

FIG. 2C is a block diagram depicting a service authentication processbetween a client and a protected server;

FIG. 2D is a block diagram depicting subsequent processing of a requestfrom a client to a protected server;

FIG. 3A is a flowchart depicting some of the steps in a process througha client obtains an identity token from a CDC in accordance with apreferred embodiment of the present invention;

FIG. 3B is a flowchart depicting some of the steps in a process throughwhich a CDC issues an identity token to a client in accordance with apreferred embodiment of the present invention;

FIG. 3C is a flowchart depicting some of the steps in a process throughwhich a client initially obtains access to a protected resource inaccordance with a preferred embodiment of the present invention;

FIG. 3D is a flowchart depicting some of the steps in a process throughwhich a client obtains access to a protected resource after alreadyreceiving a service token in accordance with a preferred embodiment ofthe present invention;

FIGS. 4A-4B are a pair of flowcharts depicting some of the steps in aprocess through which a protected server provides access to a protectedresource at the request of a client in accordance with a preferredembodiment of the present invention; and

FIG. 4C is a flowchart depicting some of the steps in a process throughwhich a CDC issues client credentials to a protected server that isgranting initial access to a protected resource on behalf of a client inaccordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a system and a methodology forsecure client-server session management. Servers that implement thepresent invention may be dispersed throughout a network. As background,a typical organization of hardware and software components within adistributed data processing system is described prior to describing thepresent invention in more detail.

With reference now to the figures, FIG. 1A depicts a typical network ofdata processing systems, each of which may contain and/or operate thepresent invention. Distributed data processing system 100 containsnetwork 101, which is a medium that may be used to providecommunications links between various devices and computers connectedtogether within distributed data processing system 100. Network 101 mayinclude permanent connections, such as wire or fiber optic cables, ortemporary connections made through telephone or wireless communications.In the depicted example, server 102 and server 103 are connected tonetwork 101 along with storage unit 104. In addition, clients 105-107also are connected to network 101. Clients 105-107 and servers 102-103may be represented by a variety of computing devices, such asmainframes, personal computers, personal digital assistants (PDAs), etc.Distributed data processing system 100 may include additional servers,clients, routers, other devices, and peer-to-peer architectures that arenot shown.

In the depicted example, distributed data processing system 100 mayinclude the Internet with network 101 representing a worldwidecollection of networks and gateways that use various protocols tocommunicate with one another, such as Lightweight Directory AccessProtocol (LDAP), Transport Control Protocol/Internet Protocol (TCP/IP),Hypertext Transport Protocol (HTTP), Wireless Application Protocol(WAP), etc. Of course, distributed data processing system 100 may alsoinclude a number of different types of networks, such as, for example,an intranet, a local area network (LAN), or a wide area network (WAN).For example, server 102 directly supports client 109 and network 110,which incorporates wireless communication links. Network-enabled phone111 connects to network 110 through wireless link 112, and PDA 113connects to network 110 through wireless link 114. Phone 111 and PDA 113can also directly transfer data between themselves across wireless link115 using an appropriate technology, such as Bluetooth™ wirelesstechnology, to create so-called personal area networks (PAN) or personalad-hoc networks. In a similar manner, PDA 113 can transfer data to PDA107 via wireless communication link 116.

The present invention could be implemented on a variety of hardwareplatforms; FIG. 1A is intended as an example of a heterogeneouscomputing environment and not as an architectural limitation for thepresent invention.

With reference now to FIG. 18, a diagram depicts a typical computerarchitecture of a data processing system, such as those shown in FIG.1A, in which the present invention may be implemented. Data processingsystem 120 contains one or more central processing units (CPUs) 122connected to internal system bus 123, which interconnects random accessmemory (RAM) 124, read-only memory 126, and input/output adapter 128,which supports various I/O devices, such as printer 130, disk units 132,or other devices not shown, such as a audio output system, etc. Systembus 123 also connects communication adapter 134 that provides access tocommunication link 136. User interface adapter 148 connects various userdevices, such as keyboard 140 and mouse 142, or other devices not shown,such as a touch screen, stylus, microphone, etc. Display adapter 144connects system bus 123 to display device 146.

Those of ordinary skill in the art will appreciate that the hardware inFIG. 1B may vary depending on the system implementation. For example,the system may have one or more processors, including a digital signalprocessor (DSP) and other types of special purpose processors, and oneor more types of volatile and non-volatile memory. Other peripheraldevices may be used in addition to or in place of the hardware depictedin FIG. 1B. The depicted examples are not meant to imply architecturallimitations with respect to the present invention.

In addition to being able to be implemented on a variety of hardwareplatforms, the present invention may be implemented in a variety ofsoftware environments. A typical operating system may be used to controlprogram execution within each data processing system. For example, onedevice may run a Unix® operating system, while another device contains asimple Java® runtime environment. A representative computer platform mayinclude a browser, which is a well known software application foraccessing hypertext documents in a variety of formats, such as graphicfiles, word processing files, Extensible Markup Language (XML),Hypertext Markup Language (HTML), Handheld Device Markup Language(HDML), Wireless Markup Language (WML), and various other formats andtypes of files.

With reference now to FIG. 1C, a network diagram illustrates a morespecific, yet generic, Web-based environment in which the presentinvention may be implemented. In this environment, a user of a browser152 at client 150 desires to access a protected resource or protectedservice on web application server 154 in DNS domain 156 or on webapplication server 158 in DNS domain 160 through a network. The computernetwork may be the Internet, an intranet, or other network, as shown inFIG. 1A, and the server may be a Web application server, a serverapplication, a servlet process, or the like.

A service may be considered to be a type of resource, and a resource maybe provided via a service; hence, service and resource may be usedinterchangeably. A protected resource is a resource, such as anapplication, an object, a document, a page, a file, executable code, orother computational resource, communication-type resource, etc., that isonly retrieved or accessed if the requesting client or user has beenboth authenticated and authorized. A protected resource, which istypically identified by a Uniform Resource Locator (URL), or moregenerally, a Uniform Resource Identifier (URI), can only be accessed byan authenticated and authorized user. Each DNS domain may have anassociated authentication server, shown as server 162 and server 164.Typically, once the user is authenticated by the authentication server,a cookie may be set and stored in a cookie cache in the browser.

As noted above, the present invention may be used within a variety ofnetworks and hardware/software platforms. More particularly, though, thepresent invention provides a methodology for secure client-serversession management using cookies. The term “cookie”, “token”, or“identifier” may be used interchangeably in relation to the presentinvention, as is described below with respect to the remaining figures.

With reference now to FIG. 2A, a block diagram shows the primaryentities that are involved in an environment that implements the presentinvention. Cookie Distribution Center (CDC) 202, providesauthentication, secure session management, and authorization credentialacquisition services to protected servers in the CDC environment, i.e.domain 200. In FIG. 2A, client 204 represents a browser session of auser at a client machine. To initiate a secure session withinCDC-protected domain 200, the client authenticates to the CDC and, ifsuccessful, receives a single-use domain cookie that represents theclient's identity for operations within domain 200, which is equivalentto stating that the domain cookie represents the client's identity foroperations with respect to the CDC alone, as will be explained in moredetail further below.

Protected server 206 hosts protected services and protected resourcesthat are sought by clients. In other words, protected server 206 may beviewed as a protected resource to client 204. To the CDC, however,protected server 206 is an authenticated client because protected server206 also uses the CDC concurrently with client 204, as is describedbelow in more detail; to the protected server, the CDC is anauthenticating server.

It should be noted that the data format of any of the messages betweenthe entities in the network, such as requests and responses, may varydepending upon system implementation in accordance with proprietary orstandard formats. It should also be noted that the CDC, the protectedserver, and/or a client may be hosted on the same physical machine.

Tokens can be classified into two types: domain tokens and servicetokens. Domain tokens represent a client identity to a secure domain,and service tokens represent a client identity to a specific service,but both domain tokens and service tokens can be implemented as a cookiein accordance with the protocols for obtaining and setting cookies for aclient browser. A domain token may be used with any service within adomain that recognizes the domain token, but a service token is specificto the service from which it was obtained; a service token may not beused with any services other than the one that created it.

The data format of any tokens may vary depending upon systemimplementation in accordance with proprietary or standard formats. Forexample, a token may also include an optional timestamp for publiclyindicating and limiting the useful lifetime of the token. A token may beformatted as a binary string, as an encoded ASCII string, or in someother interpretable format. A token may be optionally formatted inaccordance with various standards, such as PKCS (Public Key CryptographyStandards) specifications for enveloped data. In other words, inaddition to comprising hashed user-specified identity information, anyinformation within a token may be encrypted to hide the information soas to limit the risk that it might be misappropriated. It should benoted either that the entire token can be an encrypted data item or thatindividual data items can be encrypted and then placed within the token.

Protected server 206 is able to respond to service requests from client204, i.e. protected server 206 establishes a session context in which itwill provide service to client 204. However, protected server 206initially generates a request to CDC 202 and establishes a sessioncontext between protected server 206 and CDC 202. A protected servermust be known and trusted by the CDC before the protected server can beprovided service by the CDC. To that end, protected server 206 hasestablished its own session context with CDC 202 prior to a clientreceiving access to a protected resource at the protected server. Inaddition, the protected server may have established a shared session keywith which to protect communications between itself and the CDC; theentities within the network may share or synchronize cryptographic keysas appropriate in accordance with many well-known manners in the priorart.

With reference now to FIG. 2B, a block diagram depicts a domainauthentication process between a client and a CDC. As a first step,client 204 sends a login request 210 to CDC 202. Communications betweenclient 204 and CDC 202 may be protected through the use of cryptographickeys as appropriate for a selected level of security.

Assuming that the present invention is being implemented in alightweight manner, the login request may be a simple request to accessa markup language document that represents a login Web page. In thismanner, the client does not require a login application to have beenpreviously installed, and the present invention can rely on a browserapplication on the client machine to support the login process. Inresponse to the login request, CDC 202 sends a login applet 212 and arandomly generated nonce value to client 204. The login applet comprisescryptographic functionality to create a message authentication code(MAC) from the client to the server. In general, a nonce value is aserver-supplied value, such as a hexadecimal string, that is returned bythe receiving client in its response to the server in some manner. Withthe support of the browser application, the login applet would challengethe user at the client for a user identifier and a user password, andthe login applet would generate the MAC by cryptographically combiningor hashing the user-supplied information and the nonce value in anappropriate manner.

Client 204 then sends MAC 214 to CDC 202, which attempts to authenticatethe client response. If the authentication is unsuccessful, then afailure message may be returned to the client and displayed for theuser. However, assuming that the authentication is successful, then asingle-use domain token 216, i.e. a domain cookie, is returned to theclient, and an appropriate message may be returned and displayed for theuser. The browser application would store the single-use domain tokenfor subsequent use as necessary for accessing protected resources, andthe domain authentication process would be complete.

As noted previously, at some point in time, protected server 206 isrequired to complete a successful authentication process in order toestablish a session with CDC 202 before the protected server can processrequests from a client. Rather than operating the protected server in alightweight manner with respect to the CDC, a login application may beinstalled on the protected server, and the login application providesthe cryptographic functionality that is required for generating theresponses to the authentication challenges from the CDC. In that case, aprotected server would receive a nonce value from the CDC but would notreceive a login applet as part of the response from the CDC. Forexample, the login application may automatically perform its domainauthentication process with the CDC during its initialization proceduresat startup. In a manner similar to the client, if the protected serveris successfully authenticated, then the protected server also receives asingle-use domain token that is to be used with subsequentcommunications to the CDC.

With reference now to FIG. 2C, a block diagram depicts a serviceauthentication process between a client and a protected server. As afirst step, client 204 sends a request 220 for a protectedservice/resource to protected server 206. Because the protected serveris within the same domain 200 as CDC 202, the client's browserapplication sends any cookies associated with the domain in the requestor along with the request in some form of association between the domaintoken and the request; in this case, the client sends single-use domaintoken 216 that was received from CDC 202 during its domainauthentication process as described above with respect to FIG. 2B.

In response to receiving the request from the client, protected server206 then sends user/client authorization credential request 222 to CDC202. The client authorization credential request comprises the client'ssingle-use domain token and may include other secondary clientauthentication information, such as the client's IP address, whichassumes that the protected server has the ability to obtain a clientmachine's IP address independent of the token itself. In order toidentify itself to the CDC, the protected server also sends theprotected server's single-use domain token to the CDC.

Communications between protected server 206 and CDC 202 may be protectedthrough the use of cryptographic keys as appropriate for a selectedlevel of security, such as the session keys that were previouslymentioned. The protected server may use well-known authorization schemesfor obtain the client authorization credentials, such as the AuthAPI™specification, which is the Open Group Authorization API. The protectedserver can use the client authorization credentials to bind an identityto the client's session, to create a service token for the client, andto represent the client in access control decision requests via anAuthAPI™ product.

In response to receiving the client credential request, the CDCvalidates both the client's single-use domain token and the protectedserver's single-use domain token and then generates the clientcredentials, which might contain various types of information, such asauthorization information for the client or user for indicating thetypes of resources that the client or the user may access. In general,the client credentials may comprise any user-specific or client-specificauthorization information that is managed outside of a protected serverbut that may be used by a protected server to perform access controldecisions with respect to service requests to access protectedresources.

In addition, the CDC refreshes the client's single-use domain token andthe protected server's single-use domain token. As should be apparentfrom the terminology of the present invention, the single-use domaintoken can be asserted and used only once by its owning entity, i.e. theentity with which the domain token is associated. After a single-usedomain token has been used, it cannot be re-used without being refreshedor updated by its issuing entity so that it may be used again.Essentially, a token is reissued upon each use. Asserting a stale orinvalid token would result in a failed operation and optionally othersecurity measures, such as tracking the originating address of theasserting entity.

If the domain tokens have been successfully validated, then the CDCreturns the newly generated client credentials and the refreshed domaintokens to the protected server in an appropriate response message 224.Otherwise, the response indicates some type of failure upon which theprotected server may take further action.

Protected server 206 then stores the client credentials and theprotected server's refreshed single-use domain token. After otherpossible processing steps for client request 220, such as establishing asession context for client 204, protected server 206 then generates,i.e. issues, a single-use service token, which is expected to beasserted by the client along with each request that the client sends tothe protected server in order to identify the client to the protectedserver. The token also includes session information in some manner forallowing the protected server to identify the client's session contextwhen a next request is received from the client within the establishedsession. For example, a session ID can be issued by the protected serverand inserted in the service token; the session ID is subsequentlymatched to the client's session context when received by the protectedserver. Preferably, the session information is a session key containedin the data field of the cookie. Protected server 206 then returns toclient 204 a newly generated service response message 226, whichcomprises (or is otherwise associated with) an updated single-use domaintoken from the CDC, a single-use service token from the protectedserver, and any other information that fulfills the request from theclient.

With reference now to FIG. 2D, a block diagram depicts subsequentprocessing of a request from a client to a protected server. As a firststep, client 204 sends a request 230 for a protected service/resource toprotected server 206. Given the destination domain of the request, theclient's browser application sends any cookies associated with thedomain along with the request. In this case, assuming that the clienthas received refreshed tokens from the protected server in response to aprevious request, the client sends the refreshed single-use domain tokenfor domain 200 that was received from protected server 206 during theprevious request as described above with respect to FIG. 2C. Inaddition, the client also sends a single-use service token that waspossibly newly generated during the previous request as described abovewith respect to FIG. 2C.

In response, the protected server uses the session ID in the servicetoken to match the previously established session context with theclient, and the protected server processes the client's request and alsorefreshes the single-use service token. The protected server thengenerates and returns service response message 232 for the client thatcomprises the refreshed single-use service token in addition to anyother information that fulfills the client's request. Hence, anysubsequent request from a client would comprise a refreshed single-useservice token rather than a newly generated service token.

In a preferred embodiment, prior to returning a response to client 204,protected server 206 also refreshes the client's domain token byforwarding it to CDC 202; in order to do so, protected server 206 alsosends its domain token along with the client's domain token in requestmessage 234. After CDC 202 validates and refreshes the tokens, they arereturned in message 236.

In a manner similar to that described above for the single-use domaintoken, a single-use service token can be asserted only once by itsowning entity, i.e. the entity with which the service token isassociated. After a single-use service token has been used, it cannot bere-used without being refreshed or updated by its issuing entity so thatit may be used again. Essentially, a token is reissued upon each use.Asserting a stale or invalid token would result in a failed operationand optionally other security measures, such as tracking the originatingaddress of the asserting entity.

If a request from a client to a protected server does not include asingle-use domain token, the protected server can redirect the client tothe CDC to perform a login process in a manner similar to that describedabove with respect to FIG. 2B. The protected server can indicate areturn URI to which the client should be subsequently redirected aftersuccessfully completing the login process. Hence, request 210 andresponse 216 may contain information for redirecting the client asappropriate. Assuming that the HTTP protocol is being used forcommunication between the entities shown in FIG. 2D, the protectedserver may use an HTTP Redirect message. An HTTP Redirect allows aserver to respond to a client request with instructions to load aresource at a different location, and in response, most browsers willautomatically request the new resource in response to a redirect. Whenthe browser receives the HTTP Redirect, the browser issues a new HTTPRequest using the redirected URI provided in the HTTP Redirect.

With reference now to FIG. 3A, a flowchart depicts some of the steps ina process through which a client obtains a domain token from a CookieDistribution Center (CDC) in accordance with a preferred embodiment ofthe present invention. The process begins with the client initiating alogin process with a CDC (step 302), after which the client receives anauthentication challenge from the CDC (step 304). In response, theclient then sends user-specific or client-specific authentication datato the CDC in a secure manner (step 306), and the client subsequentlyreceives a domain token, i.e. domain cookie, from the CDC (step 308).The client stores the domain token (step 310) until it is required to beasserted as proof-of-identity at some later point in time, and theprocess is complete.

With reference now to FIG. 3B, a flowchart depicts some of the steps ina process through which a CDC issues a domain token to a client inaccordance with a preferred embodiment of the present invention. Theprocess begins with the CDC detecting the initiation of a login sequenceby a client in some manner (step 322), and the CDC responds by sendingan authentication challenge to the client (step 324). The CDC thenreceives user-specific or client-specific authentication data from theclient (step 326). The CDC authenticates the client or user (step 328)by processing the authentication data to determine whether or not theclient or the user that is asserting itself has properly established itsidentity, and if so, then the CDC generates a domain token for theclient or user (step 330), which might include registering the domaintoken within a database. The CDC then sends the domain token to theclient (step 332), and the process is complete.

With reference now to FIG. 3C, a flowchart depicts some of the steps ina process through which a client initially obtains access to a protectedresource in accordance with a preferred embodiment of the presentinvention. The process begins with the client generating a servicerequest to access a protected resource at a protected server (step 342).The client then sends the service request to the protected server alongwith any tokens that are associated with the domain containing theprotected server, which in this case would include the client's domaintoken that was received from the CDC (step 344). At some later point intime, the client receives from the protected server a service responsealong with a refreshed domain token and a newly issued service token,which contains some form of a session identifier (step 346). The clientstores the tokens that it has received from the protected server (step348), e.g., within a cookie cache. The client then processes any datathat has been received as part of the service response (step 350), andthe process is complete.

With reference now to FIG. 3D, a flowchart depicts some of the steps ina process through which a client obtains access to a protected resourceafter already receiving a service token in accordance with a preferredembodiment of the present invention. The process shown in FIG. 3D issimilar to that shown in FIG. 3C, but FIG. 3C represents the actions ofa client while initiating a session with a protected server, whereasFIG. 3D represents the actions of a client after a session has beenestablished with a protected server.

The process begins with the client generating a service request toaccess a protected resource at a protected server (step 362). The clientthen sends the service request to the protected server along with anytokens that are associated with the domain containing the protectedserver, which in this case would include the client's domain token thatwas received from the CDC and the client's service token (containing asession identifier) that was received from the protected server when asession was established between the client and the protected server(step 364). At some later point in time, the client receives from theprotected server a service response along with a refreshed service tokenand possibly a refreshed domain token (step 366). The client stores theupdated service token (and updated domain token, if necessary) that ithas received from the protected server (step 368), e.g., within a cookiecache. The client then processes any data that has been received as partof the service response (step 370), and the process is complete.

With reference now to FIGS. 4A-4B, a pair of flowcharts depict some ofthe steps in a process through which a protected server provides accessto a protected resource at the request of a client in accordance with apreferred embodiment of the present invention. Referring to FIG. 4A, theprocess begins with the protected server receiving a service requestfrom a client (step 402). A determination is then made as to whether ornot the service request comprises a domain token (step 404). If not,then the client is redirected to perform a login process at a CDC (step406), after which the CDC will redirect the client to the protectedserver.

If the service request comprises a domain token, then a determination ismade as to whether the service request also comprises a service token(step 408). If so, then the protected server validates the client'sservice token (step 410), and assuming the validation is successful, theprotected server refreshes the client's service token (step 412); thesession identifying information in the service token allows theprotected server to match the previously established session contextwith the client and to update or refresh the client's session context,i.e. to perform any necessary session management. In an alternativeembodiment, the protected server also sends the client's domain token tothe CDC to refresh the client's domain token; in order to do so, theprotected server would also send its domain token, which would also berefreshed. In response to the client's service request, the protectedserver then generates a service response (step 414) and sends theservice response with the refreshed service token to the client (step416), and the process is complete.

If the service request does not comprise a service token as determinedat step 408, then process branches to attempt to issue a service tokenfor the client. Referring to FIG. 4B, the protected server generates acredential request (step 422) and sends the credential request to a CDCwith the client's domain token and the protected server's domain token(step 424); other secondary authentication information may also beincluded. Assuming that the CDC successfully authenticates the submitteddomain tokens, the protected server receives the client's credentialsalong with a refreshed client domain token and a refreshed protectedserver domain token (step 426). The protected server then stores theclient's credentials (step 428); the client's credentials compriseauthorization information for making access control decisions withrespect to protected resources on behalf of the client's servicerequests.

The protected server then stores its refreshed domain token (step 430)and generates a service token for the client while establishing asession context for the client (step 432). Since this portion of theprocess is complete, the process branches back to the steps shown inFIG. 4A.

With reference now to FIG. 4C, a flowchart depicts some of the steps ina process through which a CDC issues client credentials to a protectedserver that is granting initial access to a protected resource on behalfof a client in accordance with a preferred embodiment of the presentinvention. The process begins with the CDC receiving a credentialrequest along with the client's domain token and the protected server'sdomain token (step 442). The CDC validates the protected server's domaintoken (step 444) and validates the client's domain token (step 446), andassuming that the tokens are successfully validated, the CDC generatesthe client credentials (step 448). The CDC then refreshes the protectedserver's domain token (step 450) and refreshes the client's domain token(step 452). The CDC sends the client credentials with the refresheddomain tokens to the protected server (step 454), and the process iscomplete.

The advantages of the present invention should be apparent in view ofthe detailed description of the invention that is provided above. Thepresent invention provides secure session management using single-usetokens, also termed single-use cookies. After a single-use token hasbeen issued to an entity, it may be presented for use only once, afterwhich the token must be updated or refreshed prior to re-use, therebycausing the token to be essentially reissued upon each use. Thesingle-use token contains a session identifier of some type that allowsthe token issuer to perform session management with respect to the ownerof the token. The present invention is relatively easy to implementbecause it uses standard Internet-based and Web-based protocols withoutrequiring signed applets or browser plug-ins to support the ongoing useof single-use cookies by a client. Additionally, the present inventionis independent of the encryption infrastructure that might be used tosupport secure communication between the interacting entities.

Through a server-based cookie refresh process, the present inventionprovides server-based management and control of the client securitycontext. Separate domain cookies and service cookies can be implemented,yet the method is uniform for both clients and protected servers.

It is important to note that while the present invention has beendescribed in the context of a fully functioning data processing system,those of ordinary skill in the art will appreciate that the processes ofthe present invention are capable of being distributed in the form ofinstructions in a computer readable medium and a variety of other forms,regardless of the particular type of signal bearing media actually usedto carry out the distribution. Examples of computer readable mediainclude media such as EPROM, ROM, tape, paper, floppy disc, hard diskdrive, RAM, and CD-ROMs and transmission-type media, such as digital andanalog communications links.

The description of the present invention has been presented for purposesof illustration but is not intended to be exhaustive or limited to thedisclosed embodiments. Many modifications and variations will beapparent to those of ordinary skill in the art. The embodiments werechosen to explain the principles of the invention and its practicalapplications and to enable others of ordinary skill in the art tounderstand the invention in order to implement various embodiments withvarious modifications as might be suited to other contemplated uses.

1. A method for controlling access to protected resources within a distributed data processing system, the method comprising: using a processor configured to perform data processing operations; receiving at a first server from a client a first single-use domain token associated with said client and a request to access a protected resource; validating said single-use domain token; generating a client authorization credential request; sending to a second server said client authorization credential request, said first single-use domain token, and a second single-use domain token associated with said first server, wherein said first server and said second server are operated within a common domain; receiving a single-use service token from said second server, said single-use service token associated with said client; processing said single-use service token to generate a response to said request; refreshing said single-use service token; and providing said response and said refreshed single-use service token to said client.
 2. The method of claim 1, wherein said first server: refreshes said first single-use domain token; and provides said refreshed first single-use domain token to said client.
 3. The method of claim 1, wherein said first single-use domain token comprises session information for performing session management with respect to said client.
 4. The method of claim 3, wherein said session information comprises a session key.
 5. The method of claim 1, further comprising: receiving a login request from said client at said second server; challenging said client to provide authentication data; receiving said authentication data; processing said authentication data to authenticate said client; generating said first single-use domain token; generating an authentication response; and providing said authentication response and said first single-use domain token to said client.
 6. The method of claim 5, further comprising: determining that said login request is a redirected request from said first server; and modifying said authentication response to redirect said client to said first server.
 7. A system comprising: a processor; a data bus coupled to the processor; and a computer-readable medium embodying computer program code, the computer-readable medium being coupled to the data bus, the computer program code maintaining persistent links to information stored on a network and comprising instructions executable by the processor and configured for: using a processor configured to perform data processing operations; receiving at a first server from a client a first single-use domain token associated with said client and a request to access a protected resource; validating said single-use domain token; generating a client authorization credential request; sending to a second server said client authorization credential request, said first single-use domain token, and a second single-use domain token associated with said first server, wherein said first server and said second server are operated within a common domain; receiving a single-use service token from said second server, said single-use service token associated with said client; processing said single-use service token to generate a response to said request; refreshing said single-use service token; and providing said response and said refreshed single-use service token to said client.
 8. The system of claim 7, wherein said first server: refreshes said first single-use domain token; and provides said refreshed first single-use domain token to said client.
 9. The system of claim 7, wherein said first single-use domain token comprises session information for performing session management with respect to said client.
 10. The system of claim 9, wherein said session information comprises a session key.
 11. The system of claim 7, further comprising: receiving a login request from said client at said second server; challenging said client to provide authentication data; receiving said authentication data; processing said authentication data to authenticate said client; generating said first single-use domain token; generating an authentication response; and providing said authentication response and said first single-use domain token to said client.
 12. The system of claim 11, further comprising: determining that said login request is a redirected request from said first server; and modifying said authentication response to redirect said client to said first server.
 13. A computer program product on a non-transitory computer-readable medium embodying computer program code for controlling access to protected resources within a distributed data processing system, the computer program code comprising computer executable instructions configured for: using a processor configured to perform data processing operations; receiving at a first server from a client a first single-use domain token associated with said client and a request to access a protected resource; validating said single-use domain token; generating a client authorization credential request; sending to a second server said client authorization credential request, said first single-use domain token, and a second single-use domain token associated with said first server, wherein said first server and said second server are operated within a common domain; receiving a single-use service token from said second server, said single-use service token associated with said client; processing said single-use service token to generate a response to said request; refreshing said single-use service token; and providing said response and said refreshed single-use service token to said client.
 14. The computer-readable medium of claim 13, wherein said first server: refreshes said first single-use domain token; and provides said refreshed first single-use domain token to said client.
 15. The computer-readable medium of claim 13, wherein said first single-use domain token comprises session information for performing session management with respect to said client.
 16. The computer-readable medium of claim 15, wherein said session information comprises a session key.
 17. The computer-readable medium of claim 13, further comprising: receiving a login request from said client at said second server; challenging said client to provide authentication data; receiving said authentication data; processing said authentication data to authenticate said client; generating said first single-use domain token; generating an authentication response; and providing said authentication response and said first single-use domain token to said client.
 18. The computer-readable medium of claim 17, further comprising: determining that said login request is a redirected request from said first server; and modifying said authentication response to redirect said client to said first server.
 19. The computer-readable medium of claim 13, wherein the computer executable instructions are deployable to a client computer from a server at a remote location.
 20. The computer-readable medium of claim 13, wherein the computer executable instructions are provided by a server on an on-demand basis. 